1. Field of Endeavor
The present invention relates to communications and more particularly to a time reversal communication system.
2. State of Technology
U.S. Pat. No. 5,155,742 for a time dispersion equalizer receiver with a time-reversal structure for TDMA portable radio systems to Sirikiat Ariyavisitakul and Hamilton Arnold provides the following background information, “Although the performance (i.e., low block error rate) of a receiver in a TDM/TDMA portable digital radio communications system using a time reversal phase equalizer structure for very high bit rate data communications will not be as high as a receiver using a time reversal conventional DFE structure, its performance for expanding coverage areas at moderate bit rates expected in voice communications has been experimentally found to be acceptable and is simpler to implement than receivers using conventional equalization techniques without the time reversal structure.”
U.S. Pat. No. 5,428,999 for a method and apparatus for acoustic examination using time reversal to Fink, Mathias provides the following background information, “A method for acoustic examination of a medium and detection of reflective targets includes a preliminary step of injecting a divergent sound beam into the medium from at least one transducer. Then the echo signals reflected by the medium and received by several transducers in an array are picked up. A time gate is used to select echoes coming from a particular zone of the medium. The echoes are stored, time-reversed and re-emitted. The signals newly reflected by the medium are stored and the time-reversal operation is repeated. After a final time reversal of rank 2n+1 (where n is a positive non-zero integer) over the full depth of the measurement time gate, the characteristics of the wavefront passing closest to the maxima of the signals are determined, advantageously in the form of a time distribution of the maxima. The characteristics can often be approximated with a polynomial law. An apparatus is disclosed for implementing the method.”
U.S. Patent Application No. 2001/0037075 published Nov. 1, 2001 entitled “Method and Apparatus for Dynamic Focusing of Ultrasound Energy” by James V. Candy, assigned to the Regents of the University of California, provides background information regarding using a methodology to obtain time series measurement data (or “data”) reconstructing an inhomogeneous medium using time-reversal (T/R) focusing, “When a wave propagates through a spatio-temporal medium (e.g., tissue), the resulting wavefront is distorted. This distortion is related to the medium as well as the type of source creating this phenomenon. If a media is homogenous, then its sound velocity profile, density/temperature profile, index of refraction or related velocity function is independent of spatial position. An inhomogeneous medium possesses an inherent property related to velocity that does vary with spatial position. If the medium is homogenous and the source resides in the near field, then a spherical-type wavefront evolves. But if the medium is inhomogeneous, then a distorted wavefront results. In the homogenous medium, simple time-delay processing is sufficient to enhance the field at a given point; however, this is not necessarily the case in an inhomogeneous medium, since the amplitude as well as the phase may be distorted during propagation.”